The d2 spectrometer as originally developed for air pollution measurement will be modified and improved for use in the measurement of ammonia in the blood and breath of human subjects. The absorption cell will be designed to be evacuated, for observation of ammonia content in blood samples vaporized into the vacuum. For breath ammonia determinations, the cell will be used at normal pressure, but it will be heated to prevent water condensation from the breath. Two instruments will be fabricated. Two research programs will be carried forward in parallel, utilizing the instruments, in the College of Medicine, in addition to a continuing program of exploration in the Engineering college. Task 1, in Engineering, will focus on exploration of capabilities of the instrument for measurement of other gases than ammonia, accumulation of statistics on normal breath ammonia content, and possible extension of applications for measurement of amino acid content of biological samples. Task 2, in the Department of Physiology, will be directed at the study of ammonia content in the breath as a function of the state of the body, exertion, rate of breathing, etc., using the measurement of ammonia as a means of further understanding the respiratory processes. Task 3, in the Department of Renal Medicine of the College of Medicine, will involve measurements of ammonia in blood, breath, spinal fluid, etc., in connection with clinical practice involving nephritic patients, as well as cases involving liver failure, etc. The objective will be to explore the details of management of ammonia by the human body.